TABLE OF CONTENTS Antenna gain and effective area
Remarkable utility of the paraboloid
Deriving the antenna far-field antenna gain pattern with calculus
Design features for mainbeams and sidelobes
Unique features of arrays
Several ways to steer the beams of phased arrays, emphasizing phase shifters
An antenna is the mechanism by which the electromagnetic signal is radiated and received. For radars (although not necessarily for antennas in other electromagnetic applications), it is essential that the antenna enhance performance. A radar antenna has three roles: to be a major contributor to the radar s detection performance, to provide the required surveillance, and to allow measurements of angle of sufficient accuracy and precision.
A reasonable place to begin is with the two expressions used in Chapter 1 to derive the radar range equation: antenna gain and effective area. For a transmitting antenna, antenna gain is simply a measure of how much focusing of the transmitted waveform is being accomplished by the antenna. Focusing is the ability to add up energy preferentially. Energy arriving at the antenna from a given direction is integrated; that arriving from elsewhere is not. It is assumed that energy arriving at the antenna is in the form of plane waves, that is, the phase of the arriving energy is constant over any plane perpendicular to the direction of arrival, as shown in Figure 2.1. Because most sources of electromagnetic energy are small, these wavefronts are really spherical, but at ranges of...
